Cellular Structures and Function
History of the cell
Robert Hooke – English – first discovered
cells, 1665-cork
Anton von Leeuvenhoek – Dutch – pond
water – animalcules (little animals)
Matthias Schleiden – German botonist– cells
plants, composed of units called cells
Theodor Schwann - German zoologist – all
animals compare
Modern Cell Theory
1. Cells are the smallest complete living
things – basic units of organization
2. All organisms are composed of one or
more cells in which all life process occur
3. Cells arise only from preexisting cells
through the process of cell division
4. All of today’s existing cells are
descendants of the first cells
Cells in general
50-100 trillion cells
260 cells varieties
Differentiated – cells with specialized
characteristics, distinctive shape for
function
Measured in mircrometer, 10-6 m
Composite cells
3 parts of a cell:
Cell membrane – outermost limit,
defines cell, thin, selectively
permeable, signal transduction,
message response
Cytoplasm
Nucleus (eurkaryotic) – typical,
membrane bound, Prokayrotic –
lacks, bacteria
Cell Membrane Molecule structure:
Phospholipids bilayers
Cell membrane, plasma membrane,
plasmalemma
Double phospholipid layer with proteins.
Phosphorus – blue balloon, hydrophillic
(attracts water)
Lipid – purple tails, hydrophobic (repels
water)
Proteins form channels to allow passage of
molecules (facilitated diffusion), pores
Fluid mosaic pattern
Proteins
Integral – spans the cell membrane
Peripheral – projects from surface
Transmembrane – in cytoplasm
project through cell membrane, coiled
– receptors
Cellular adhesion – molecule (CAM) –
cells touch / bind, glycoprotein – “self”
CAMS
Some cells must move, ex. White
blood cells
Selectin – covers WBC, provide
traction as nearing injury site
Integrin – allows WBC to stick to
injury site where it will destroy
bacteria.
Cytoplasm
Protoplasm – liquid part (of cell)
Cytoplasm (cytosoll)– outside nucleus
Nucleoplasm – inside nucleus
Water, solution – individual atom distributed
throughout
Colloid – clumps of atoms distributed though
out medium
Cytoskeleton – protein rod / tubules for
support
Cellular Organelles
There are several reasons why cells
evolved organelles. First, organelles can
perform specialized functions (cilia, these
short filaments act as "paddles" to help
some cells move).
Second, membrane bound organelles can
act as containers, separating parts of the
cell from other parts of the cell.
Third, the membranes of organelles can
act as sites for chemical reactions.
Cellular Organelles
Nonmembrane Bound OrganellesRibosome's
Centrioles
Microtubules
Membrane Bound OrganellesNucleus
Mitochondria
Lysosomes
Endoplasmic reticulum
Golgi Apparatus
Peroxisomes
Nucleus
Control center of the cell,double nuclear
membrane (envelope). Nucleoplasm fluid
in the nucleus. Membrane has pores to
allow material out (mRNA).
Nucleic acid called chromatin found. They
shorten and thicken during cell division.
Nucleolus – spherical particle in
nucleoplasm where ribosomes are made
(synthesized).
Mitochondria
Powerhouse of the cell. Composed of
two membranes. Inner folds called
cristae. Where anerobic cellular
respiration occurs. Cells with higher
energy requirements have more
mitochondria (muscles)
DNA passed on by mother
Lysosomes
Small structures in cytoplasm
surrounded by membrane and contain
digestive enzymes.
Functions: digest stored foods (with
vacoule), repair of organelles, suicide
agents in old, weakened cells
Peroxisomes
Resembles lysosome
Found primarily in liver and kidney
Catalyzes metabolic reactions that
release hydrogen peroxide
(synthesize bile acids, breakdown
lipid, degradation of rare
biochemicals, alcohol detox
Endoplasmic reticulum
Membrane – bound channels called
cisternae
Connects outer nuclear membrane
and cell membrane, transports
Rough E.R. – attached ribosomes,
protein synthesis
Smooth (agranular) E.R. - transports
fats, synthesis of sex hormones.
Golgi apparatus, body, complex
Collection of flat saclike cisternae that
look like stack of pancakes
Compounds to be secreted are
concentrated and collected
(wrapped), act as a warehouse
Carbohydrate synthesized if cell’s job
Ribosomes
Small granules in cytoplasm and
attached to ER. (no membrane)
Proteins and RNA
Site of protein synthesis
Proteins are part of structure of
membranes, enzymes or catalyst for
reactions, immune response
Centrioles
Two centrioles are found at right
angles to each other near nuclear
membrane (pair as centrosome)
Each centriole is composed of 9 sets
of triplet fibers
Centrioles form spindle fibers during
cell division and guide the
chromosomes to their daughter cells
Cillia and Flagella
Composed of fibrils
Cillia are short, many rows; move
materials across the free surface of
cell. (respiratory tract cells)
Flagellum are long, hair like, one or
two, will propel the cell through a
medium (sperm cell)
Microfilaments and microtubules
Distinguished by protein type, diameter and
how they assemble
Microfilaments – tiny rods of protein actin,
form meshwork provide cellular movement
(myofibrils in muscle)
Microtubules – globular protein tubulin,
rigid – cell shape,
Specialized cells have intermediate
filaments which form dimers (protein pairs).
Epidermis cells attach
Inclusions
Temporary structures
Stored nutrients – glycogen and lipids
Pigments - like melanin in skin
Plant cells vs. animal cells
Plant cells have a cell wall made of
cellulose (fiber in food, not digested)
Chloroplast – green structure that are
responsible for photosynthesis.
6CO2 + 12 H2O -> C6H12O6 + 6O2 + 6 H2O
Chromoplasts – carotenoid pigments
(Xanthophyll – yellow, carotene – orange)
Leucoplast – no pigment, storage plastids
(onion bulb)
Vacuole – water storage
Cellular Diagram
Process of Protein Synthesis
Code to make a protein is a gene on a DNA
molecule.
Messenger RNA (mRNA) copies the code form DNA
in a process called transcription. mRNA leaves the
nucleus through a pore and takes the code to a
ribosome or group of ribosomes
Transfer RNA (tRNA) go into the cytoplasm and pick
up a particular amino acid. Each tRNA is coded for
Amino acid by its anti-codon loop and will only
match a particular site on the mRNA molecule called
a codon. This process is called translation
Ribosome (rRNA) will now link up Amino acid
brought to mRNA by the tRNA to form a protein.
Discovers of DNA (heredity
material of cell)
Friedrich Miescher – 1869 – German
chemist isolated the nucleic acid
P.A. Levine – 1920 – Discovered DNA
contained Phosphates, five – carbon
sugars and nitrogen bases. These form a
nucleotide
Rosalind Franklin – British – discovered the
helical structure using crystallography
James Watson – American – Francis Crick
– British – won the 1962 Nobel Prize for
working out the 3 dimensional structure
(double helix).
Anatomy of a DNA molecule
Double helical chain (twisted ladder) of
nucleotides
Nucleotides has phoshate group (PO4), Five –
carbon sugar (deoxyribose), and a nitrogen –
containing base (purine or pyrimidine)
Pyrimidine – single ring of 6 carbon atoms of C
and N.(thymine or cytosine)
Purine – fused double ring of 9 atoms of C and N.
(adenine and guanine)
Sugar and phosphate make the backbone. The
bases attach to the sugar
The Four Nitrogen Based pairs
The four nitrogen
bases are,
Adenine(A)
Guanine(G)
Thymine(T)
Cytosin(C)
Adenine bonds
with Thymine
Cytosin bonds with
Guanine
These double
nitrogen-bases
bind to form what is
known as the “DNA
Double Helix”
DNA structure
Mitosis
Cell cycle G1 – growth, S – synthesis, G2
growth, Mitosis- cellular division
Single cell duplicates itself –allows body to
growth, repair, maintain structure;
maintains our life
Mitosis is nuclear division plus cytokinesisdivision of the cytoplasm and produces two
identical daughter cells.
Prophase-chromatin shorten and darken to form
chromosomes, nuclear membrane disappears,
centrioles and spindle fibers form
Metaphase- chromosomes line up at middle,
spindle fibers attach to centromere and centrioles
Anaphase- chromosome split and move towards
poles (centrioles)
Telophase- Chromosomes at the poles
Cytokinesis – splitting of the cytoplasm (with
organelles)
Interphase is often included in discussions of
mitosis, but interphase is technically not part of
mitosis, but rather encompasses stages G1, S,
and G2 of the cell cycle.
Mitosis Diagram
Meiosis
http://cellscienceproject.tripod.com/sitebuildercont
ent/sitebuilderfiles/meiosis.mov
http://www.trentu.ca/biology/101/14.html
Increases genetic variability – offspring a chance
to adapt to changing environment
Occurs in ovaries – females, (oogenesis – ovum
sex cell), testes – male (spermatogensis – sperm
sex cell)
Reduction division of nuclear material – ½ (23
chromosomes) genetic material
Mutation – exact copy of genetic code is disrupted,
producing a variation
Meiosis
Prophase 1 – Homologous chromosomes pair and
crossing over may occur
Metaphase 1 – Homologous pairs align along
equator
Anaphase 1 – Centromere do NOT divide. Each
chromosome goes to pole
Telophase 1 – Division
Prophase 2 – Chromosome appears
Metaphase 2 – Chromosomes line up at equator
Anaphase 2 – Centromeres divide
Telephase 2 – Chromatids at pole, cytokinesis, 4
haploid cells
Meiosis diagram
Control of cell division
Telemere – tip of chromosomes,
same 6 nucleotides repeat hundreds
of times, when tip wear down – cells
stops dividing
Surface area to cell volume
Hormones and growth factors
Space availability – contact inhibition
Stem and progenitor cells
Differentiation – process of specialization
Stem cells – able to divide to give rise to
other progenitor stem cells – “self
renewing”; egg and embryo cells are
totipotent – give rise to every cell type
Progenitor cells – partially specialized stem
cells, continues specialization; pluripotent –
daughter cells follow several pathways, but
not all.
Cell death
Apoptosis – programmed cell death –
normal part of development, remove
excess skin (webbed digits) and peeling
sunburn, orderly
Not the same as necrosis – cell death due
to injury or inflammation
Cell membrane receives a signal to die –
enzyme caspases cuts up components and
cell membrane covers (blebs) and
phagocytizes
Mutations
Change in DNA that effects a person,
detectable
Most Single nucleotide polymorphisms –
change in 1 base pair, no effects.
Spontaneous – chemical tendency of
bases to exist in 2 slightly different ways.
Induced – exposed to a mutagen – agent
that causes a mutation (radiation,
chemicals.
If change is in germ line (egg or sperm
cells) mutation will be passed to offspring.
Metabolism
Total chemical changes that occur in
cells.
Anabolism – is the energy-requiring
process that builds larger molecules
from smaller
Catabolism – energy – releasing
process that breaks down larger
molecules into smaller ones.
Cellular respiration
ATP is formed from energy
breakdown in food to put together
ADP(adenosine diphosphate) and
PO4 (phosphate) to make ATP
Overall chemical equation
C6H12O6 +O2 -> 6CO2 + 6H2O + 38
ATP (36 ATP AND 2 GTP)
Cellular respiration
Glycolysis
Occurs in cytoplasm, anaerobic – doesn’t
require oxygen
Use 2 ATP molecules to start, these are “paid
back” from production of ATP
Products: Fructose diphosphate which splits into
2 phospoglyceraldehyde molecules that oxidizes
into 2 phosphoglyceric acids which converts to 2
pyruvic acids molecules
The metabolic breakdown of glucose and other
sugars that releases energy in the form of ATP.
Total net gain of 8 ATP. In anaerobic glycolysis in
muscle (lactic acid) and in fermentation (yeast
cells) only 2 ATP are produced.
Glycolysis
Krebs citric acid cycle
Aerobic – requires oxygen
Named for British Biochemist Sir
Hans Krebs in 1937
2 Pyruvic acid molecules are
converted to acetic acid then to
acetyl-Co-A through the action of CoA
enzyme. Acetyl-CoA enters cristae of
mitochondria to go through citric acid
cycle
Kreb’s cycle continued
Major products: Citric acid, alphketogluteric acid, succinic acid, malic
acid and oxaloacetic acid.
2 ATP or GTP are produced in citric
acid cycle.
14 ATP are produced for each pyruvic
acid (2 total)
Krebs cycle diagram overview
Electron Transport system
Functions as a set of reduction – oxidation
reaction
Electron carriers: NAD (nicotinamide
adenine dinucleotide) FAD (flavin adenine
dinucleotide), quinone, cytochrome system
NAD – (3 ATP) FAD – (2 ATP)
Oxygen is needed for respiration because
oxygen is the ultimate electron acceptor in
the system
Oxygen accepts electrons from 2 H atoms
to form water (H20) as a waste product